Abstract: The present invention provides methods for distinguishing between different isoamylase genes of individual genomes of a polyploid plant. These methods enable a polyploid plant-to be produced and/or identified which has at least one impaired isoamylase gene. In particular, the methods of the invention enable various plants of a polyploidy species to be produced and/or indentified which, between the plants, lack a functional isoamylase gene for each genome of the plant. Such plants can be cross-bred to produce a plant which lacks any functional isoamylase protein. Furthermore, the invention provides numerous isoamylase gene, protein and cDNA sequences from various polyploidy plant species, including hexaploid wheat.